Introduction of Encryption with DES

On 15 May 1973, the NBS (National Bureau of Standards, now called NIST – National Institute of Standards and Technology) published a request in the Federal Register for an encryption algorithm that would meet the following criteria:

• Have a high security level related to a small key used for encryption and decryption
• Be easily understood
• Not depend on the algorithm’s confidentiality
• Be adaptable and economical
• Be efficient and exportable

In late 1974, IBM proposed “Lucifer”, which, thanks to the NSA (National Security Agency), was modified on 23 November 1976 to become the DES (Data Encryption Standard). The DES was approved by the NBS in 1978. The DES was standardized by the ANSI (American National Standard Institute) under the name of ANSI X3.92, better known as DEA (Data Encryption Algorithm).

The DES Algorithm

The main parts of the algorithm are as follows:

• Fractioning of the text into 64-bit (8 octet) blocks;
• Initial permutation of blocks;
• Breakdown of the blocks into two parts: left and right, named L and R;
• Permutation and substitution steps repeated 16 times (called rounds);
• Re-joining of the left and right parts then inverse initial permutation.